Gas Volume Ratio Research Articles

High-Temperature Rheological Study of Foam Fracturing Fluids

Summary. Two significant observations were made during measurement of N2 foam properties at temperatures up to 300 degrees F [149 degrees C] in a high-temperature, high-pressure recirculating loop viscometer:foam fluids did not thin as rapidly as gel fluids under similar conditions, so foams offer inherent advantages for high-temperature stimulation work, andhigh gelling-agent concentrations do not improve dynamic foam stability; instead, high-temperature dynamic stability depends on surfactant type and concentration. Mathematical equations have been developed from experimental data to describe foam rheological behavior from 75 to 300 degrees F [24 to 149 degrees C], 0 to 80 quality, containing 0 to 80 lbm hydroxypropyl guar (HPG)/1,000 gal [0 to 9586 g HPG/m3] in the aqueous phase. Basic physical properties previously outlined determined foam rheological physical properties previously outlined determined foam rheological behavior at 75 degrees F [24 degrees C]. Foams were classified as yield-pseudoplastic-type fluids. This paper extends the previous work from 75 to 300 degrees F [24 to 149 degrees C] and covers a broader range of external liquid-phase compositions applicable to foam stimulation work. Introduction Reidenbach et al. recently outlined the basic physical properties that determine foam rheological behavior at properties that determine foam rheological behavior at 75 degrees F [24 degrees C]. Important laminar flow parameters included texture (bubble-size distribution), parameters included texture (bubble-size distribution), quality, liquid-phase properties (n and K), and yield point. Foam fluids were classified as yield-pseudoplastic point. Foam fluids were classified as yield-pseudoplastic or Herschel-Bulkley type. Because foams used for stimulation are normally used with bottomhole temperatures above 75 degrees F [24 degrees C], N2 foam properties were measured at temperatures up to 300 degrees F [149 degrees C]. Foam fluids did not thin as rapidly as base gel fluids under similar conditions. We had anticipated using n and K values for base gel fluids at elevated temperatures in the room-temperature foam equations to predict foam properties at elevated temperatures. Such calculated viscosities generally were lower than experimental viscosities at elevated temperatures. To include temperature effects properly, therefore, the original equations had to be modified. Theory The basic laminar flow equation for pressure loss of foam fluids in a pipe has been given asThe yield point, sigma yp, is a function of quality, gamma, only. Gamma is the ratio of gas volume to gas plus liquid volume at a specific temperature and pressure. For gamma less than 0.6,and for gamma greater than 0.6,The consistency index of the foam, Kf, depends on the consistency index of the liquid gel phase, KL, its quality, and a tabulated empirical constant, C1, according toIn actual use, C1 varies with liquid-phase gelling-agent concentration. The flow-behavior index, n, was assumed to be the same for both gel phase and foam. From the initial high-temperature experiments using 70-quality N2 foam and various gelling-agent concentrations, we did not know the functional relationship, if any, between yield point, consistency index, and flow-behavior index vs. temperature. It was apparent that the fluid-behavior index remained nearly constant with increasing temperature, but the consistency index decreased with increasing temperature. The effect of temperature on yield point with various gel concentrations was uncertain. Data are presented that examine the effect of these parameters on foam viscosity. Experimental Procedure The recirculating flow-loop viscometer was based on 0.305-in. [7.75-mm]-ID stainless-steel tubing. Valves in the flowline were the full-opening ball type. Fig. 1 is an outline of the flow pattern. The aqueous phase of the fluid to be tested was pumped from a 5-L pressure vessel to the loop by a metering pump. The loop was filled with liquid to a pressure of pump. The loop was filled with liquid to a pressure of 1,000 psi [6.9 MPa], as regulated by a backpressure regulator. During the filling process, fluid flowed through a mass flowmeter. Specific gravity was read to three decimal places with computer averaging. The specific gravity reading allowed foam quality to be adjusted on-line. A glass inspection gauge allowed visual inspection of the fluid. JPT p. 613

Computed tomography based estimates of regional gas and tissue volume of the lung in supine subjects with chronic airflow limitation or fibrosing alveolitis.

Twelve patients with chronic airflow limitation and 12 patients with a histological diagnosis of fibrosing alveolitis were studied. The calculated mean (SD) tissue volume of a single lung at total lung capacity was 467 (91) ml in the patients with alveolitis, which was 43% (14%) more than predicted for healthy people of the same age, sex, and height. The tissue volume of a single lung at total lung capacity was 436 (82) ml in the patients with chronic airflow limitation, which was 26% (21%) more than predicted. At residual volumes the tissue contents of the fibrotic and the obstructed lungs changed very little (to 407 (84) ml and 433 (84) ml respectively). This allowed tissue volume to be used as a marker of position within the lung, to match inspiratory and expiratory slices and to calculate regional ventilation. In both groups local ventilation was diminished and more variable than in healthy lungs--that is, in the mid 70% of lung volume the local residual volume to total gas volume ratios (RV/TGV) were 32% (10%) in the fibrotic group and 66% (14%) in the group with chronic airflow limitation, compared with 23% (5%) in healthy subjects. As expected, the fibrotic lungs were much denser (0.246 (0.036) g/ml) and the lungs with chronic airflow obstruction were less dense (0.114 (0.026) g/ml) than were healthy lungs (0.126 (0.017) g/ml).

Wide-gap boron-doped microcrystalline silicon nitride

Microcrystalline SiNx:H films were prepared by rf glow discharge of SiH4-B2H6-N2-H2 mixtures with the gas volume ratio of B2H6/SiH4=4.5×10−3. The volume fraction of the crystalline phase and the crystallite size decrease with an increase in N content x, and the films were amorphous at x above 0.2. The dark conductivity σd decreases and the optical gap Eg increases with x. The gap-state density is lowest at x near 0.2, where σd∼10−2–10−3/Ω cm (the activation energy is 0.1 eV) and Eg∼1.9 eV. These electrical properties are improved as compared with those for B-doped amorphous SiNx:H.

Electrical and optical properties of amorphous SixN1−x

Abstract Amorphous silicon nitride films have been prepared by the glow-discharge decomposition of a wide range of ammonia/silane gas mixtures. In particular, samples prepared from mixtures containing very small amounts of ammonia have been investigated. The dark- and photoconductivities, the optical gap and the thermoelectric power have been measured as a function of the volume ratio of the deposition gases, denoted by R. A range of specimens has also been prepared in a junction configuration, and the electron and hole mobilities of these has been determined. The results of all of the measurements show a systematic and continuous variation with R. Extended-state conduction predominates throughout, and the majority carriers are electrons. For R < 5 × 10−3 it is believed that a shallow level of ionized donor states is introduced. This is supported by the sensitization of the photoresponse, the decrease in the conductivity activation energy and the decrease in the electron drift mobility activation energy. ...

Control of the optical band gap of hydrogenated amorphous boron: The use of the B 2H 6–BF 3 gas mixtures

Amorphous boron thin films have been produced by the glow discharge decomposition of diborane, boron trifluoride, and hydrogen gas mixtures. The optical band gap of these films was controlled by changing the relative proportions of diborane and boron trifluoride. Films with band gaps of approximately 1.45 eV can be obtained by using a B 2H 6 : BF 3 gas volume ratio of 8 : 1 and a substrate temperature of 225°C. The electron paramagnetic resonance spectrum shows a pronounced shift in the g factor, giving evidence of fluorine incorporated into the amorphous matrix.

Foam Stimulation

Summary Foamed fluids are becoming very popular for use in stimulation treatments. This can be attributed to their excellent properties such as low leakoff rate, excellent proppant transport, longer fractures with less fluid, minimum formation damage, and superior posttreatment cleanup. Base fluids that can be foamed are oil, water. and acid. Foam quality is very critical to many of the properties of the resultant foam fluid. This quality changes with temperature and pressure. Included in this paper is a new approach to an easier determination of foam quality under bottomhole treating conditions so that necessary ratio adjustment can be made at the wellhead to obtain the desired quality at the formation. History The earliest foam fracturing treatment was performed in Jan. 1968. 1 This treatment placed approximately 2041 kg (4,500 lbm) of 12-/20-mesh glass bead proppant with an approximately 83 to 85%-quality foam to stimulate the Brown shale formation in Lincoln County, WV. Virtually no other use of foam stimulation fluids was reported until the latter half of 1973. At this time, there was a development, undercurrent of foam stimulation use that spread across the country and into Canadian operations. Papers presented by Blauer, Mitchell, and Kohlhaas in April 1974 and by Blauer and Kohlhaas in October 1974 served further to popularize this budding stimulation technique. Most foam fracturing treatments performed during 1973–76 were small volume, generally less than 189 m3 (50,000 gal), and carried some form of propping agent. Several other papers describing mechanical and design procedures for foam fracturing treatments appeared in 1975, 1976, and early 1977. Surprisingly, the site of the first massive foam stimulation treatment was the same general location as the first experimental treatment. In June 1976, a 946-m 3 (250,000-gal) foam fracturing treatment, which placed 135 715 kg, (299,200 Ibm) total sand. was performed in Lincoln County, WV. A second treatment comprising 1060 m3 (280,000 gal) foam and 140 432 kg (309,600 Ibm) total sand was performed in Nov. 1976, in the same West Virginia county. Both treatments were conducted as part of a joint Columbia Gas System Service Corp./ERDA demonstration of massive hydraulic fracturing in the Devonian shale. During, 1977–78, papers describing, variations in the established pattern in foam fracturing began to appear. Among these variations was extension of foam to fracture-acidizing applications. As a technique to reduce further the formation exposure to a potentially damaging aqueous fluid, a foamed methanol/water solution also was introduced at this time. Although there was evidence that the number of foam stimulation treatments was increasing, papers presented during 1979–80 gave an impression that this service was entering a period of consolidation or maturity. Counteracting this initial impression were several massive hydraulic fracturing services performed in cast Texas during the latter half of 1980. Treatments with volumes ranging, up to 2233 m3 (590,000 gal) of 65%-quality foam were performed. This largest job to date placed 503 487 kg (1,110,000 total lbm) of sand. Foam Quality Foam is a gas/liquid dispersion, with gas as the internal phase and liquid as the external phase. Foam quality is the ratio of gas volume to foam volume (volumetric gas content) at a given pressure and temperature. JPT P. 597^

Surface Tension and Foaming of Protein Solutions

ABSTRACTThe relationship between surface tension and foamability of protein solutions was examined. Proteins including egg albumin, soybean protein, casein, milk whey protein and gelatin were used. Foamability was expressed as “foaming power” which corresponded to the ratio of gas volume to the liquid volume in the foam. The absolute surface tensions of protein solutions were not correlated to foamability, but the rate constant of surface tension decay of protein solutions was significantly correlated to foamability of protein solution.

Pressure-temperature relationship for decomposition of sodium bicarbonate from 200 to 600.degree.F

The equilibrium dissociation pressure of initially dry sodium bicarbonate (nahcolite) was experimentally determined between 200 and 600/sup 0/F. It was found necessary to use a constant ratio of initial gas volume to solid nahcolite volume, V/sub g//V/sub s/, to obtain a unique pressure--temperature curve. Such pressure--temperature relationships were measured for three values of V/sub g//V/sub s/, each curve showing three points of discontinuous slope. For V/sub g//V/sub s/ = 1, the pressure exceeded 6000 psia above 487/sup 0/F. Since the Green River oil shale formation in Colorado contains both beds and isolated nodules of nahcolite, the pressure developed by heating nahcolite may be a factor in developing porosity and permeability during an in situ thermal process for producing shale oil.

Étude sommaire sur les inclusions fluides d'une topaze de Montbelleux (Ille-et-Vilaine)

The similarity between fluid inclusions in copper and tin porhyries has been noted in various articles, particularly by Sillitoe et al. (1975). It therefore seemed of interest to investigate ores samples from French tin mines for such inclusions. In one sample we observed, in the same crack, inclusions containing microcrystalline deposits of halite and two-phases aqueous inclusions for which the ratio of gas volume to total volume was variable as is the case in porphyry copper.

Determination of Optimum Parameters in Connection with Transportation with a Gas Stream

The specific energy consumption, and - by way of this - the expenditure of the transportation of solid, granular material with a gas stream is highly dependent on the dimensions of the transport conduit and on the working parameters. If the output of the transport system is given, the diameter of the conduit and the amount of transporting gas has to be chosen so as to obtain minimum transportation costs. This problem was solved by the introduction of intermediate variables. A method of calculation is proposed for the determination of the optimum values of the processes parameters, such as gas flow rate and volume ratio of solid. The application of the method is illustrated with the example of vertical transportation of sodium bicarbonate.

EXTRACTION FROM TWO-PHASE DROPLETS

A new spray column-type extractor, in which the gas (air) was injected from the inside tube (0.2φ I.D.) into a liquid droplet (toluene or toluene+24.5wt% CCl4) flowing from the annular space of the double tube (outside tube: 0.65φ, 1.10φ and 2.80φ I.D.), liquid droplets combined with gas bubbles ( = two-phase droplets) were formed at the tip of a nozzle, and the solute (acetic acid) in droplets was extracted with water, is proposed. The density of dispersed-phase liquid, the volume ratio of gas to oil in the two-phase droplet and the nozzle diameter were varied, and the results showed that the increase of the volume ratio of gas to oil in the two-phase droplet led to high efficiency of the extraction.

Grandientless reactors and transient methods in heterogeneous catalysis

A general review of catalytic laboratory reactors is presented which emphasizes gradient-less reactors. Details are given on a new gradientless reactor system which is well designed for transient experiments. This reactor has a low ratio of gas volume to catalyst volume. Experimental results verify that the reactor is well-mixed and free from undesirable mass and heat transfer effects under reactions conditions. The desirability and utilization of such a reactor is discussed.

Hydrogenation of triglycerides containing linolenic acids: II. Continuous hydrogenation of vegetable oils

AbstractIn this study continuous hydrogenation of neutral oils, especially the selective hydrogenation of soybean oil, is described. The reactor is a column divided by a series of plates into a number of reaction chambers. Oil with suspended catalyst and hydrogen enters the column at the bottom and flows concurrently with hydrogen through it. The pressure in the reactor will adjust itself, depending on the activity and concentration of the catalyst and throughput of oil. The ratio of gas volume in the reactor to volume of the oil is very low, so that the iodine value of the hydrogenated product can be controlled to within 1.5 iodine unit.

Two phase friction factor for para‐hydrogen between one atmosphere and the critical pressure

AbstractThe Martinelli model for pressure drop in flowing two‐phase systems has been examined in detail for para‐hydrogen from 1 atm. to its critical pressure. Amethod for obtaining the Martinelli Φ term, two phase friction factor, at intermediate pressures is presented. Φ2 can be expressed as a function of pressure and quality. The Martinelli β term, ratio of actualvapor or gas area to an idealized cylindrical area, is found to vary greatly and to indicate first an increase in gas‐liquid interface to gas volume ratio and then a decrease with increasing pressure. Some experimental data are examined in light of this development.

A preliminary study of vapor deposition of rhenium and rhenium-tungsten

Coherent, high-purity rhenium deposits were obtained by the hydrogen reduction of ReF 6 from the vapor phase, although some rhenium powder was always produced. The reaction temperature and the ratio of H 2 to ReF 6 significantly influenced the amount of coherent rhenium deposited. The near-optimum parameters are temperature, 250 °C; H 2 to ReF 6 gas volume ratio, 25. The deposition efficiency for coherent rhenium deposits was 70–75%. The average Knoop microhardness of vapor-deposited rhenium was 907, measured under a 100 g load. Intermittent deposition is undesirable for forming coherent deposits because it produces discontinuities in the metal. Codeposits of rhenium and tungsten were obtained, but they were of non-uniform composition, owing to the large difference in optimum reduction temperatures of their hexafluorides.

The Streaming Potential and the Rheology of Foam

Abstract An experimental study of the flow of fine-textured, aqueous foams through Pyrex tubes is described. The foams range in quality F (ratio of gas volume to total volume) from 0.70 to 0.96 and behave like pseudoplastic fluids. At lower flow rates they exhibit laminar flow and have apparent viscosities which increase with quality, and which cover a range of 15 cp to 255 poise for tubes of 0.25- to 1.50-mm radius ri. At higher flow rates a plug-like type of flow is developed, the extent of which increases with both and ri. When the same foams flow through either open or packed Pyrex tubes, remarkably high streaming potentials phi E are often generated. These can easily reach 50v if nonionic foaming agents are used, but are at least an order of magnitude less for ionic foaming agents. A linear relationship between phi E and the pressure differential phi p is observed; this usually extrapolates to positive values of phi p at phi E of zero. The slope of the line increases with both F and ri. An equation was derived to describe the streaming potential of non-Newtonian fluids in circular tubes and was used to correlate experimental results. The calculated potential is are of the right order of magnitude. Introduction Foams are both unusual and intriguing in their physical properties, and have been the subject of many scientific studies. However, present knowledge of foams is still fragmentary, specific and often contradictory. Apparent viscosity of foam is the physical property of greatest interest to both rheologists and engineers. Sibree reported that the apparent viscosity decreased with increasing shear rate in a manner similar to some non-Newtonian fluids. Penny and Blackman reported that fire-fighting foams had both a limiting shear stress and a tensile yield stress. There is little doubt that some foams at least behave like non-Newtonian fluids, and have apparent viscosities considerably higher than those of either constituent phase. The high apparent viscosity of foam with its concomitant effect on mobility ratio and sweep efficiency no doubt prompted several attempts by research groups to use foam as a displacing agent in porous media. Based on recent experience, most of these groups probably succeeded in completely blocking fluid flow in the porous media and then abandoned their efforts. Two groups apparently found the successful combination of experimental parameters at about the same time. Others have recently added to our knowledge-of foam flow in porous media and its use as a displacing agent. An experimental problem encountered by Fried was a transient blockage of foam flow in porous media when distilled water was used to prepare the foam-producing solution. Fried surmised that this was due to an electrokinetic effect and he eliminated it by using electrolytes in preparing foaming solutions. He also measured the streaming potential of a number of foams in capillary tubes which he found to be appreciably higher than those obtained when the constituent liquid flowed under comparable conditions. This paper presents results of a more comprehensive study of the streaming potential generated by aqueous foam flowing in both open and packed Pyrex tubes. It also adds to knowledge of the rheology of these foams as deduced from their flow behavior in open tubes. APPARATUS AND PROCEDURE A diagram of the apparatus used is shown in Fig. 1. Details of its construction, testing and use are described elsewhere. Careful selection of materials, extreme cleanliness and rather elaborate electrical insulation and shielding were necessary to obtain reproducible results (15 percent). Both streaming potential and streaming current were measured with an electrometer. The design of the foam generator developed for this work is novel (Fig. 2). SPEJ P. 359ˆ

The Flow of Foam Through Short Porous Media And Apparent Viscosity Measurements

Abstract Externally generated foam was injected continuously into short porous media. Both flow rate and pressure drop were measured. Liquid saturation was determined by electrical conductivity. Foam quality G, expressed as the ratio of gas volume to total volume, was varied from 0.70 to 0.96. As measured with a modified Fann VG Meter, apparent viscosity of this foam µa decreases with increasing shear rate but usually falls within the range of 50 to 500 cp. At a given shear rate, µa increases almost linearly with G. When measured with a Bendix Ultraviscoson, kinematic µa is independent of r but absolute µa increases with r from about 3 to 8 cp. The effective permeability-apparent viscosity ratio ke/µa decreases almost linearly with G for porous media of high permeability, but the rate of decrease becomes less for tighter ones. The relative permeability-apparent viscosity ratio kr/µa vs G data does not fall on a single line. The kr/µa ratio increases with liquid saturation in the porous medium and with surfactant concentration. Estimates of µa for foam in porous media vary from 30 to 100 cp. INTRODUCTION Although research on the development of a foam-drive, oil recovery process has been going on for almost a decade, most of the significant publications have appeared within the last several years. This illustrates well the rate at which interest in this process is accelerating. Bond and Holbrook1 were the first to describe the use of foam to improve oil recovery in their patent of 1958. They proposed that an aqueous foaming agent slug be injected into the formation and that this be followed by gas to produce a foam in situ. Fried2 studied the injection of foam into porous media which has already been subjected to conventional gas or water drives and found that gas could be used to drive a foam bank which would, in turn, displace additional oil in the form of an oil bank. He attributed the increased oil recovery to the high effective viscosity of foam flowing in porous media. His microscopic observations showed the importance of foam generation and regeneration within the porous medium. By injecting both air and aqueous surfactant solution, Bernard3 generated foams within the porous medium in which oil displacement was being studied. In a separate empirical test, he also measured the dynamic foaming characteristics of the same surfactants in water and/or oil. With some exceptions and for the seven surfactants studied, there seems to be a qualitative relationship between the efficiency of liquid displacement and the dynamic foaming test used. This relationship was not consistent enough to eliminate the necessity of actual foam flood tests in porous media for surfactant selection. In a study basic to gas storage in aquifers, Bennett4 described the displacement of brine by foam in consolidated porous media. Among other things, he stated that the ability of a surfactant solution to foam is more important than the stability of its foam. The presence of a foam bank between the displacing air and the displaced brine improved both breakthrough and ultimate recovery. In a continuation of this work Kolb5 attributed the great reduction in surfactant solution production rate as displacement by air progressed to a decrease in relative permeability to gas. These several effects reported by both Bennett and Kolb can all be attributed to the high apparent viscosity of foam which was obviously flowing in the porous media.

On the Propagation of Sound in a Liquid Containing Gas Bubbles

The theory of the propagation of sound in a homogeneous gas including the effect of heat conduction is presented for the purpose of clarifying the underlying thermodynamic process. The propagation of sound in a liquid with a homogeneous and isotropic distribution of gas bubbles is then considered. The bubbles are assumed to be sufficiently small and numerous so that the mixture can be taken to be a uniform medium. The effect of heat conduction is included. If f is the ratio of gas volume in the mixture to liquid volume, it is shown for the range of f of general interest that the acoustic condensations and rarefactions of the gaseous portion of the medium are essentially isothermal. It is also found that the attenuation of an acoustic disturbance by heat conduction is quite small.

混合ガス (天然ガス+CO2) による鉄鉱石の還元について

In the previous reports (ib., Tetsu-to-Hagane Vol.41, 1955, p.5-11; Vol.41, 1955, p.1149-4155), the authors reported the experiment on the reduction process of iron are by natural gas, and it was recognized that the reduction power of the gas was very strong when its decomposition was found. Then it was found that its decomposition was increased with increase of the reducing degree of iron are too.Then, the authors examined the reformation of natural gas by CO2 gas and the reduction of iron are by its reformed gas.Results obtained were as follow;(1) The reforming ratio was varied from 60 to 90% by the reducing degree of iron sand pellets which were fixed in the reforming furnace.(2) Using the unreduced iron sand pellets, the reforming ratio at 850°C was greater than at 900, 950°C.(3) Using completly reduced pellets, the reforming ratio was 90% of more.(4) When the volume ratio (CH4: CO2) of mixed gas was about 1: 1, reforming ratio was greatest and the reduction of iron are by reforming mixed gas was rapid, and the degree of reduction reached 90-100%.

Flow Resistance of Gas-oil Mixtures through Vertical Pipes

The resistance to flow of mixtures of gas and oil in passing up through theflow tubing of oil wells operated by gas-lift or by natural flow is a factor inoil-recovery technic that has received but little attention. Yet accuratedesign of a tubing installation for a particular set of conditions, whereoperation is by either of these methods, is impossible without quantitativedata on the pressure loss suffered by the oil-gas mixture in its passagethrough the well tubing to the surface. Because of lack of such information, petroleum production technologists have been compelled to approach this problemby "cut-and-try" methods, which, doubtless in many cases, has resultedin the installation and use of tubing too large or too small for most efficientutilization of the expansive force of the gas used in lifting the oil.Impressed with the necessity for information of this character, the authorshave conducted a series of tests with large-scale apparatus in the petroleumengineering laboratories of the University of California, designed to beproductive of data that would.afford a means of attacking the problem offlow-tubing design on a more scientific basis. Mechanics of Expulsion of Gas-Oil Mixtures in Naturally Flowing and Gas-LiftWells When oil is lifted from a well by the expansive force of compressed natural gasor air, the fluids enter the lower end of the eduction tube under elevatedpressure, with the gas partly in solution, but largely distributed in the formof occluded bubbles within the oil mass. As discharged from deep wells, afterreaching the surface, there will normally be at least 60 times as much gas, byvolume, as of oil; and in many cases the ratio of gas volume to that of the oilwill have a value as great as 1000 or more. On entering the lower end of theeduction tube, however, a relatively smaller volume of gas will be found in theoil-gas mixture, on account of compression of the gas in accordance with theelevated pressure necessary.